linux-kernel - Re: [PATCH v6 14/34] x86/mm: Insure that boot memory areas are mapped properly

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Date:   Mon, 12 Jun 2017 08:31:58 -0500
From:   Tom Lendacky <thomas.lendacky@....com>
To:     Borislav Petkov <bp@...en8.de>
Cc:     linux-arch@...r.kernel.org, linux-efi@...r.kernel.org,
        kvm@...r.kernel.org, linux-doc@...r.kernel.org, x86@...nel.org,
        kexec@...ts.infradead.org, linux-kernel@...r.kernel.org,
        kasan-dev@...glegroups.com, linux-mm@...ck.org,
        iommu@...ts.linux-foundation.org, Rik van Riel <riel@...hat.com>,
        Radim Krčmář <rkrcmar@...hat.com>,
        Toshimitsu Kani <toshi.kani@....com>,
        Arnd Bergmann <arnd@...db.de>,
        Jonathan Corbet <corbet@....net>,
        Matt Fleming <matt@...eblueprint.co.uk>,
        "Michael S. Tsirkin" <mst@...hat.com>,
        Joerg Roedel <joro@...tes.org>,
        Konrad Rzeszutek Wilk <konrad.wilk@...cle.com>,
        Paolo Bonzini <pbonzini@...hat.com>,
        Larry Woodman <lwoodman@...hat.com>,
        Brijesh Singh <brijesh.singh@....com>,
        Ingo Molnar <mingo@...hat.com>,
        Andy Lutomirski <luto@...nel.org>,
        "H. Peter Anvin" <hpa@...or.com>,
        Andrey Ryabinin <aryabinin@...tuozzo.com>,
        Alexander Potapenko <glider@...gle.com>,
        Dave Young <dyoung@...hat.com>,
        Thomas Gleixner <tglx@...utronix.de>,
        Dmitry Vyukov <dvyukov@...gle.com>
Subject: Re: [PATCH v6 14/34] x86/mm: Insure that boot memory areas are mapped
 properly

On 6/10/2017 11:01 AM, Borislav Petkov wrote:
> On Wed, Jun 07, 2017 at 02:15:39PM -0500, Tom Lendacky wrote:
>> The boot data and command line data are present in memory in a decrypted
>> state and are copied early in the boot process.  The early page fault
>> support will map these areas as encrypted, so before attempting to copy
>> them, add decrypted mappings so the data is accessed properly when copied.
>>
>> For the initrd, encrypt this data in place. Since the future mapping of the
>> initrd area will be mapped as encrypted the data will be accessed properly.
>>
>> Signed-off-by: Tom Lendacky <thomas.lendacky@....com>
>> ---
>>   arch/x86/include/asm/mem_encrypt.h |   11 +++++
>>   arch/x86/include/asm/pgtable.h     |    3 +
>>   arch/x86/kernel/head64.c           |   30 ++++++++++++--
>>   arch/x86/kernel/setup.c            |    9 ++++
>>   arch/x86/mm/mem_encrypt.c          |   77 ++++++++++++++++++++++++++++++++++++
>>   5 files changed, 126 insertions(+), 4 deletions(-)
> 
> Some cleanups ontop in case you get to send v7:

There will be a v7.

> 
> diff --git a/arch/x86/include/asm/mem_encrypt.h b/arch/x86/include/asm/mem_encrypt.h
> index 61a704945294..5959a42dd4d5 100644
> --- a/arch/x86/include/asm/mem_encrypt.h
> +++ b/arch/x86/include/asm/mem_encrypt.h
> @@ -45,13 +45,8 @@ static inline void __init sme_early_decrypt(resource_size_t paddr,
>   {
>   }
>   
> -static inline void __init sme_map_bootdata(char *real_mode_data)
> -{
> -}
> -
> -static inline void __init sme_unmap_bootdata(char *real_mode_data)
> -{
> -}
> +static inline void __init sme_map_bootdata(char *real_mode_data)	{ }
> +static inline void __init sme_unmap_bootdata(char *real_mode_data)	{ }
>   
>   static inline void __init sme_early_init(void)
>   {
> diff --git a/arch/x86/mm/mem_encrypt.c b/arch/x86/mm/mem_encrypt.c
> index 2321f05045e5..32ebbe0ab04d 100644
> --- a/arch/x86/mm/mem_encrypt.c
> +++ b/arch/x86/mm/mem_encrypt.c
> @@ -132,6 +132,10 @@ static void __init __sme_map_unmap_bootdata(char *real_mode_data, bool map)
>   	struct boot_params *boot_data;
>   	unsigned long cmdline_paddr;
>   
> +	/* If SME is not active, the bootdata is in the correct state */
> +	if (!sme_active())
> +		return;
> +
>   	__sme_early_map_unmap_mem(real_mode_data, sizeof(boot_params), map);
>   	boot_data = (struct boot_params *)real_mode_data;
>   
> @@ -142,40 +146,22 @@ static void __init __sme_map_unmap_bootdata(char *real_mode_data, bool map)
>   	cmdline_paddr = boot_data->hdr.cmd_line_ptr |
>   			((u64)boot_data->ext_cmd_line_ptr << 32);
>   
> -	if (cmdline_paddr)
> -		__sme_early_map_unmap_mem(__va(cmdline_paddr),
> -					  COMMAND_LINE_SIZE, map);
> +	if (!cmdline_paddr)
> +		return;
> +
> +	__sme_early_map_unmap_mem(__va(cmdline_paddr), COMMAND_LINE_SIZE, map);
> +
> +	sme_early_pgtable_flush();

Yup, overall it definitely simplifies things.

I have to call sme_early_pgtable_flush() even if cmdline_paddr is NULL,
so I'll either keep the if and have one flush at the end or I can move
the flush into __sme_early_map_unmap_mem(). I'm leaning towards the
latter.

Thanks,
Tom

>   }
>   
>   void __init sme_unmap_bootdata(char *real_mode_data)
>   {
> -	/* If SME is not active, the bootdata is in the correct state */
> -	if (!sme_active())
> -		return;
> -
> -	/*
> -	 * The bootdata and command line aren't needed anymore so clear
> -	 * any mapping of them.
> -	 */
>   	__sme_map_unmap_bootdata(real_mode_data, false);
> -
> -	sme_early_pgtable_flush();
>   }
>   
>   void __init sme_map_bootdata(char *real_mode_data)
>   {
> -	/* If SME is not active, the bootdata is in the correct state */
> -	if (!sme_active())
> -		return;
> -
> -	/*
> -	 * The bootdata and command line will not be encrypted, so they
> -	 * need to be mapped as decrypted memory so they can be copied
> -	 * properly.
> -	 */
>   	__sme_map_unmap_bootdata(real_mode_data, true);
> -
> -	sme_early_pgtable_flush();
>   }
>   
>   void __init sme_early_init(void)
>